FI64248C - OIL COUPLING FOER STYRNING AV BILDAOTERGIVNING OCHISYNNERHET VAEXELSTROEMS-ELEKTROLUMINENSAOTERGIVNING - Google Patents

Description

64248

The present invention relates to a method according to the preamble of claim 5 1. The invention also relates to a coupling used for the application of this method.

The AC electroluminescence display based on thin film technology comprises a two-dimensional matrix of X and Y electrodes for the control circuits, where the X electrodes form rows and the Y electrodes in turn form columns.

It is further typical of such a display that the control voltage is AC, the DC component in the control voltage reduces the lifetime of the display by 15, the required modulation voltage is less than half the control voltage, the luminance typically decreases with a time constant of about 1 ms and the capacitance is high. about 50 ... 200 pF / mm.

To describe the state of the art, reference should be made to the following publications: (1) Gielow T.A., Holly R.H .: "Tactical video display", 25 Report number DELET -TR-79-0251-1, Sept. 1980, 17 p.

(2) Kurahashi K., Takahara K., Andoh Sh. : "A Refresh Addressing Technique of AC-TFEL Panels", Proceedings of the First European Display 30th Research Conference EURODISPLAY '81, September 16-18, 1981, Munich, pp. 216 ... 219, and (3) FI Patent Application 8112 U 5 (Oy Lohja Ab)

In the method according to the publication (1), each row in turn receives a high-amplitude row selection-35 pulse while the other rows float. The columns are simultaneously supplied with a modulation voltage of 64248 z corresponding to the desired luminance. After the row selection pulses, all rows are simultaneously given a reciprocating refresh pulse. In this solution, it has been possible to reduce the voltage resistance required of the column driving circuits 5 to a voltage of one-sided modulation.

The method described in the reference publication (2) corresponds to the previous method in terms of voltage resistance. The methods differ in that in the previous 10 method high voltage pulses are applied to the ground point of the row drive circuits and the ground point of the column drive circuits is connected to the ground point of the entire control system. In the method according to the reference publication (2), the ground point of the row driving circuits is connected to the system ground and the high voltage pulses 15 are applied to the ground point of the column driving circuits.

Reference (3) discloses a method by which the voltage resistance requirement of columnar circuits can be reduced by applying bipolar pulses to the rows and applying modulation to both positive and negative control pulses on the display.

All of the above recreational methods require high voltage driving circuits to control the row electrodes. As is known, high voltage circuits are difficult to integrate and therefore expensive. The methods according to reference publications (1) and (2) also have the disadvantages of the presence of a direct voltage component in the control voltage of the display and the high voltage resistance required of the column driving circuits due to one-sided modulation. The need for two different driving circuits is also a significant drawback.

It is an object of the present invention to obviate the disadvantages of the prior art systems. It is also an object of the invention to provide a recreational method for controlling an AC electroluminescent display, especially based on thin film technology, which lowers the voltage endurance requirements for 3 64248 display circuits, reduces display power consumption and enables a completely DC component-free control voltage. It is a further object to provide a coupling for the application of the method.

The invention is based on e.g. to the following thoughts:

Most preferably, the capacitances of the entire display are charged to the highest possible base voltage, however, so that the row selection or column modulation pulses alone are not sufficient to ignite any display element.

The row voltage and column modulation voltage are deposited on top of the base voltage so that the voltage of the non-muted display elements does not change, the absolute value of the voltage of the half-selected display elements increases by no more than * the row selection or column modulation voltage .

20 - The polarity of the reference voltage is preferably changed only after all the rows have in turn received the row selection pulse.

The device has two DC voltage sources, one is the operating voltage source for the row driving circuits and the other is the operating voltage source for the column driving circuits.

In addition, the device has an AC power supply connected in series with another DC power supply.

More specifically, the method 30 according to the invention is characterized by what is set forth in the characterizing part of claim 1.

The connection according to the invention is in turn characterized by what is set forth in the characterizing part of claim 7.

The invention provides considerable advantages.

64248 k

Thus, the voltage resistance required for both in-line and column driving circuits is only equal to the maximum value of the modulation voltages, about 30 V. Previous recreational methods have required a voltage resistance of about 5 60 V for column driving circuits and about 200 V for row driving circuits. The reduction of the voltage resistance requirement facilitates integration and leads to cheaper and more reliable circuits.

Both driving circuits can be similar, 10 which reduces the number of circuit types to be integrated.

The monitor control voltage does not include a DC component, which increases the life of the monitor.

The power consumption of the display is small because the amplitude of the row selection and column modulation pulses is small and because the frequency of the 15 base voltages can be small, even less than 25 Hz.

Only one high-voltage AC voltage source is required for the connection, whereas in previous solutions up to four pulse sources have generally been required. This 20 lowers the price of the device and improves reliability.

The invention will now be examined in more detail by means of an exemplary embodiment according to the accompanying drawings.

Figure 1 shows one circuit according to the invention applied to a 2x2 matrix display.

Fig. 2 shows graphically the time course of the different control pulses related to the switching according to Fig. 1.

In Figure 1, the display matrix comprises rows X1 and X2 and columns Y1 and Y2. Display items C11, C12, C21, and C22 are located at the intersection of rows and columns-30. In the case of the elements, the voltages measured from the X electrodes to the Y electrodes are denoted UC11, ^ cip '^ C21 * ^ a respectively UC22 * The ground point SE of the column driving circuits SA is preferably connected to the ground point 35 JE of the entire control system. The ground point RE of the in-line driving circuits RA is connected to the AC voltage U_ generated by the AC voltage source B.

U

5 64248

In Fig. 2, it is assumed that the display element C22 is in the display state corresponding to the maximum luminance and that the voltage URM acting across the row driving circuits RA, which is in series with the alternating voltage UR, is equal to the voltage UgM acting across the column driving circuits SA * Then URM = UgM = UM ·

Consider the formation of the control voltages of the display elements C11, C12, C21 and C22 at the moment when line X2 is selected. When U ,. is positive, the selected o 10 line X2 receives the voltage UR + UR ^ when the non-selected line X1 receives the voltage UR. At the same time, the selected column Y2 is connected to the mass point SE and the non-selected column Y1 to the voltage UgM> The positive amplitude of the basic voltage (ugjAg) is thus formed by subtracting the AC voltage from the positive peak value U of the column modulation

D

the maximum value of the voltages U_w, When IL · is negative, SM ώ the selected line X2 is connected to the voltage -UR and the non-selected a line to the voltage -IL · + U_ „. The selected column Y2 is now connected to the voltage UgM and the non-selected column Y1 to 20 ground, so that the negative amplitude of the basic voltage (UgjAg) is the absolute value of the AC voltage peak.

A

value IL · minus the line selection voltage IL ·, ..

D KM

It can be seen from Figure 2 that when selecting the row selection voltage UBU and the maximum value of the column modulation voltages U_u KM is equal to 25 (UgM = URM = UM), the voltage of all display elements C11, C12, C21, C22 is AC voltage with peak values 0D at half-selected displays.

D

with items C11, C12, C21 and UR + UM on the selected display item C22. It can also be seen from Figure 2 that when the line X2 receives 30 selection pulses, the display element C11 is not selected and thus receives only a fundamental voltage (UR ^ g) with an absolute value of amplitude UR - U ^.

Within the scope of the invention, it is also possible to consider solutions that differ from the embodiment described above.

Thus, in contrast to the example of Figures 1 and 2, it is possible to change the polarity of the base voltage more frequently than after each field. It is possible to increase the frequency up to several periods per line.

5 The row selection voltage URM and the maximum value of the column modulation voltages Ug ^ are equal in the example of Figures 1 and 2. They can also be different sizes. The symmetry of the control voltage can then be maintained by selecting the AC voltage IL ·

D

10 positive and negative amplitudes by the difference between the row value of the row selection voltage and the maximum value of the column modulation voltages UgM as different.

In the example of Figures 1 and 2, the non-selected rows are always connected to either the positive or negative terminal of the selection voltage source RM of the row-15 according to the phase of the AC voltage Ug. If the line selection voltage IL ·., Is selected

x \ M

at least twice the maximum value of the column modulation voltages Ug ^, non-selected rows may be allowed to float when the selected row receives a selection-20 pulse. This reduces power consumption.

Contrary to the example of Fig. 1, it is possible to use a bridge connection in such a way that unipolar pulses with respect to the system ground are applied to the terminal RE, SE of both the row and column drive circuits RA and SA with respect to each other.

The example of Figures 1 and 2 deals with the case where the luminance of the display elements has only two levels. It is clear that the method according to the invention can also be used in connection with image displays.

In addition to burst length and pulse width modulation, amplitude modulation can also be used to control the luminance, for example as stated in the reference (3), by silencing the column modulation voltage corresponding to the desired luminance between zero and the maximum value UgM 35.

Claims (11)

7 64248 A method for controlling an image display and in particular a two-dimensional thin-film alternating current electroluminescent display (C11, C12, C21, C22) comprising 5 matrices (XI, X2; Y1, Y2) consisting of X and Y electrodes, according to which the row selection pulses are applied to the X electrodes (X1, X2) in turn and the column modulation pulses corresponding to the desired luminance are applied to the Y electrodes (Y1, Y2), characterized in that at least some of the display elements (C11, C12, C21, 15 C22) is allocated to the highest possible base voltage of variable polarity ^ UBIAS ^ 'j ° ka is selected so that the row selection or column modulation pulses alone are not sufficient to ignite any display element 20 (C 1 1, C12, C21, C22), and a line is layered on the base voltage. and column modulation voltages selected so that only the sum of the basic voltage (), the row selection voltage (U ^) 25 and the column modulation voltage puts each selectable element (C11, C12, C21, C22) into display mode. A method according to claim 1, wherein the AC voltage source (B) is connected in series with a line selection voltage source (RM) 30, characterized in that the basic voltage (Ug 1 g) is formed from the AC voltage (Ug) by subtracting the line selection voltage (U) if the AC voltage is negative. , and RM o is the maximum value of the column modulation voltages (Ug ^) if the 35 AC voltage (Ug) is positive. 8 64248 A method according to claim 1, wherein the alternating voltage source (B) is connected in series with the column modulation voltage source (SM), characterized in that the basic voltage (Ug 1 g) is formed from the alternating voltage (Ug) by subtracting the line selection voltage (URM) if the alternating voltage (Ug) is positive, and the maximum value of the column modulation voltages (U011) if the AC voltage (ΙίΏ) is negative. Method according to Claim 1, characterized in that the polarity of the basic voltage (Ug 1 g) is changed only after all the rows (XI, X2) have in turn received a row selection pulse. Method according to Claim 1, characterized in that the row selection voltage (U 1) used and the maximum value (Uou) of the column modulation voltages are equal to one another. SM Method according to Claim 1, characterized in that the row selection voltage (URM) used and the maximum value of the column modulation voltages (Ug 1) are different, the symmetry of the control voltage being maintained by selecting the positive and negative amplitudes of the AC voltage (Ug) between the row selection voltage and the column modulation voltages. (URM> UgM) difference. A circuit for use in applying the method according to claim 1, comprising a thin-film AC-electric current display (C11, C12, C21, C22) based on a matrix (X, X2; Y1, Y2) of X and Y electrodes. ), row driving circuits (RA) for supplying row selection pulses alternately to X electrodes (X1> X2), 35. column driving circuits (SA) for supplying column modulation pulses to Y electrodes (Y1, Y2), 9 64248 row selection voltage source (RM), row selection voltage (RM), „) For generating, πΜ M column modulation of a column modulation voltage source (SM) for generating voltages, 5 characterized in that the row selection voltage source (RM) and the column modulation voltage source (SM) are DC voltage sources and the connection includes a base voltage (UgIAg) connected in series with either a row selection voltage source (RM) or a column modulation voltage source (SM), whereby different voltage sources (B, RM, S M) the voltages 15 are chosen so that the basic voltage (UBT.J is formed iii. Ab symmetrically and so that, on the one hand, the row selection or column modulation pulses alone superimposed on the base voltage (UgiAg) are not sufficient to ignite any display element (C11, C12, C21, C22), but on the other hand only the sum of the base voltage C11, C12, C21, C22) display mode. Connection according to Claim 7, characterized in that the direct voltages (URM, UgM, UM) generated by both the row selection and the column modulation voltage source (RM, SM) are equal. Connection according to Claim 7, characterized in that the alternating voltage source (B) is connected in series with the line selection voltage source (RM). Connection according to Claim 9, characterized in that the ground point (SE) of the column modulation voltage source (SM) is at the same potential as the ground point (JE) of the alternating voltage source (B). 10 64248 Pat entkrav: